Tablet integrated liquid crystal display apparatus with less parallax

ABSTRACT

In a tablet integrated type liquid crystal display apparatus, a first transparent substrate is provided on a view side. The first substrate is a plastic substrate having a thickness equal to or thinner than 0.6 mm, and a counter electrode is formed on the first substrate. A second substrate on which a driving layer composed of switching elements and pixel electrodes respectively connected to the switching elements is formed. The second substrate is a glass substrate having a thickness in a range of 0.6 mm to 1.1 mm. A guest host liquid crystal layer sandwiched by the first substrate and the second substrate such that the guest host liquid crystal is driven by a voltage applied between the counter electrode and the pixel electrode. A tablet electrode layer may be provided between the first substrate and the counter electrode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of patent application Ser.No. 09/393,025, filed Sep. 9, 1999 now issued as U.S. Pat. No. 6,295,101which is a divisional application of U.S. Ser. No. 08/778,268, filedJan. 2, 1997 now U.S. Pat. No. 5,995,172.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display apparatus andmore particularly to a tablet integrated liquid crystal displayapparatus in which a tablet input apparatus and a liquid crystal displayapparatus are integrated.

2. Description of Related Art

The apparatus that a tablet input apparatus and a display apparatus areunified is known as an input apparatus to input an instruction or datato a computer. In this apparatus, the instruction or data is inputted bydirectly touching the tablet input apparatus.

For example, as shown in FIG. 1, a display apparatus 12 and a tablet 13are formed independently, and they are made as a unitary apparatus. Inthis example, as a display apparatus, a liquid crystal display apparatusis used, and as a tablet, a resistive film type tablet is used in whicha small gap is provided between two resistive film sheets connected to apower supply and current flowing when an input pen 1 is used to contactthe two resistive film sheets each other is detected so that the contactposition is detected.

Next, FIG. 2 is a cross sectional view illustrating the structure of thetablet integrated type liquid crystal display apparatus shown in FIG. 1.In FIG. 2, a reference numeral 15 is a tablet, 16 and 17 are a set ofpolarizers, 18 and 19 are an opposing glass substrate and a thin filmtransistor (TFT) glass substrate, and 20 is a twisted nematic type(hereinafter, to be referred to as a “TN type”) liquid crystal. Areference numeral 21 is a backlight which functions as a light source.

In a conventional active matrix driving type liquid crystal displayapparatus, glass substrates having the thickness of about 0.6 to 1.1 mmare used as the substrates which sandwich the liquid crystal. Therefore,there is a problem in that the conventional liquid crystal displayapparatus is heavy because the thick glass substrate is used. However,it is difficult to make the thickness of the glass substrate thin in theviewpoint of mechanical strength.

On the other hand, in a case where a pen input type screen inputapparatus is combined with such a liquid crystal display apparatus, whenan instruction or data is inputted by contacting the input pen 14 withthe screen input apparatus, there is a problem in that the thickness ofthe viewing-side glass substrate directs a parallax between a tip of aninput pen 14 and a liquid crystal display image so that it is not easyto input the instruction or data. In order to eliminate the parallax, iffilm substrates having the thickness of about 0.1 mm are used, when afilm is deposited on the substrate on which switching elements areformed, there is a case that the substrate bends due to stress becausethe substrate is thin. Also, there is another problem in that thesubstrate is bent on handling it so that the switching elements aredamaged.

Generally, in a display apparatus using a TN liquid crystal, when thelayer width of the TN liquid crystal is changed due to external force,the angle of torsion of the TN liquid crystal is changed at the portionwhere the external force is applied, such that the transmissivityremarkably changes. Therefore, in a case where a tablet integratedliquid crystal display apparatus is fabricated to have the structureshown in FIG. 2 using the TN liquid crystal, there is a problem in that,when the input pen 14 is pushed to the tablet 15 for input of aninstruction or data, the layer width of the TN liquid crystal is changedat the portion where the input pen 14 is pushed and the peripheralportion, so that the transmissivity changes there. As a result, thedisplay quality is degraded there.

In order to solve this problem, as shown in FIG. 3, a method is known inwhich a transparent glass or plastic protecting board 23 is insertedbetween the tablet 15 and the liquid crystal display apparatus 22 toprevent influence to the liquid crystal display apparatus 22 due to theforce by the input pen 14. However, in order to prevent the layer widthof the liquid crystal in the display apparatus 22 in a case of usingthis method, it is necessary that the protecting board 23 is notdeformed due to the pushing force. For this reason, the protecting boardneeds to be thick and firm. As a result, there is a problem in that thetablet integrated type liquid crystal display apparatus becomes heavyand thick. Also, because the distance between the tip of the input pen14 and a liquid crystal display image is widened to several mm or more,there is a problem of the parallax that the image is displayed on theposition which is different from the tip of the input pen 14.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a tabletintegrated type liquid crystal display apparatus in which the parallaxbetween the tip of an input pen and a display image is eliminatedwithout occurrence of the bending of a substrate and the damage of aswitching element.

In order to achieve an aspect of the present invention, a tabletintegrated type liquid crystal display apparatus includes a firsttransparent substrate provided on a view side, wherein the firstsubstrate has a thickness equal to or thinner than 0.6 mm, and wherein acounter electrode is formed on the first substrate, a second substrateon which a driving layer composed of switching elements and pixelelectrodes respectively connected to the switching elements is formed,and guest host liquid crystal layer sandwiched by the first substrateand the second substrate such that the guest host liquid crystal isdriven by a voltage applied between the counter electrode and the pixelelectrode.

In the tablet integrated type liquid crystal display apparatus, a tabletelectrode layer may be provided between the first substrate and thecounter electrode such that the tablet electrode layer is isolated fromthe counter electrode. Alternatively, a tablet electrode layer may beprovided on the first substrate on an opposite side of the counterelectrode. In this case, it is preferable that a protecting film isprovided on the tablet electrode layer. In addition, a tablet electrodelayer may be provided between the second substrate and the driving layersuch that the tablet electrode layer is isolated from the driving layer.

The tablet integrated type liquid crystal display apparatus may be atransmission type or a reflection type. In case of the reflection type,the pixel electrodes functions as reflecting plates in addition to thedriving of the guest host liquid crystal. Also, it is preferable thatthe first substrate is a plastic substrate and the second substrate is aglass substrate having a thickness in a range of 0.6 mm to 1.1 mm.

In order to achieve another aspect of the present invention, a tabletintegrated type liquid crystal display apparatus includes a firsttransparent substrate provided on a view side, wherein a counterelectrode is formed on the first substrate, a second substrate on whicha driving layer composed of switching elements and pixel electrodesrespectively connected to the switching elements is formed, a pluralityof insulative supports provided between the first substrate and thesecond substrate to prevent the first substrate from being bent, andliquid crystal layer sandwiched by the first substrate and the secondsubstrate such that the liquid crystal is driven by a voltage appliedbetween the counter electrode and the pixel electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a conventional tablet integrated typeliquid crystal display apparatus before assembly;

FIG. 2 is a cross sectional view of the tablet integrated type liquidcrystal display apparatus shown in FIG. 1;

FIG. 3 is a cross sectional view illustrating the structure of amodification of the tablet integrated type liquid crystal displayapparatus shown in FIG. 1;

FIG. 4 is a cross sectional view illustrating the structure of atablet-integrated-type liquid crystal display apparatus according to thefirst embodiment of the present invention in which a transmission type,TN liquid crystal type, TFT driving type, and active matrix type liquidcrystal display apparatus is used;

FIG. 5 is a cross sectional view illustrating the structure of atablet-integrated-type liquid crystal display apparatus according to thesecond embodiment of the present invention in which a reflection type,phase-transition guest host (GH) liquid crystal type, TFT driving typeand active matrix type liquid crystal display apparatus is used;

FIG. 6 is a cross sectional view illustrating a tablet integrated typeliquid crystal display apparatus according to the third embodiment ofthe present invention;

FIG. 7 is a circuit diagram illustrating the circuit of the a tabletintegrated type liquid crystal display apparatus in the thirdembodiment;

FIG. 8 is a graph showing the dependency of transmissivity of a liquidcrystal layer upon voltage applied across the liquid crystal layer whenthe layer width of the liquid crystal layer is changed due to pushingpressure;

FIG. 9 is a cross sectional view illustrating a tablet integrated typeliquid crystal display apparatus according to the fourth embodiment ofthe present invention;

FIG. 10 is a cross sectional view illustrating a tablet integrated typeliquid crystal display apparatus according to the fifth embodiment ofthe present invention;

FIG. 11 is a cross sectional view illustrating a tablet integrated typeliquid crystal display apparatus according to the sixth embodiment ofthe present invention;

FIG. 12 is a cross sectional view illustrating a tablet integrated typeliquid crystal display apparatus according to the seventh embodiment ofthe present invention;

FIG. 13 is a cross sectional view illustrating a tablet integrated typeliquid crystal display apparatus according to the eighth embodiment ofthe present invention; and

FIG. 14 is a cross sectional view illustrating a tablet integrated typeliquid crystal display apparatus according to the ninth embodiment ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, the tablet integrated type liquid crystal display apparatus of thepresent invention will be described with reference to the accompanyingdrawings.

First, a tablet integrated type liquid crystal display apparatusaccording to the first embodiment of the present invention will bedescribed. FIG. 4 is a cross sectional view of the structure of thetablet integrated type liquid crystal display apparatus in the firstembodiment. In the first embodiment, a twisted nematic (TN) liquidcrystal is used for a transmission type display apparatus. The TN liquidcrystal is driven by thin film transistors (TFTs) in an active matrixsystem.

Referring to FIG. 4, a TFT substrate 19 is composed of a glass substratehaving the thickness of 0.6 to 1.1 mm. On a surface of the TFT substrate19, a plurality of gate bus lines and a plurality of drain bus lines arearranged in a lattice manner by a usual process for producing a TFTsubstrate. A TFT 32 as a switching device and a pixel electrode 31 areprovided for each of intersections of the plurality of gate bus linesand the plurality of drain bus lines. The TFT 32 is formed by a usualmethod including a plasma CVD method for deposition of an amorphoussilicon (a-Si) film. As a result, the TFTs 32 are provided in a matrixmanner on the glass substrate 19.

A counter electrode substrate 26 is composed of a film substrate havingthe thickness of 0.1 mm. Polyether sulfone or polyethylene terephtalateis used as the material of the film substrate 26. The thickness of thefilm substrate 26 is preferably equal to or less than 0.6 mm and morepreferably equal to or less that 0.2 mm. A tablet electrode layer 27 ofITO is formed on the surface of the film substrate 26 opposing the glasssubstrate 19. An insulating film 28 is formed on the whole surfaceincluding the tablet electrode layer 27 and then a counter electrode 29of ITO is arranged on the insulating film 28 corresponding to the pixelelectrode 31.

The TFT substrate 19 and the film substrate 26 are subjected to arubbing process for orientation processing, after an orientating filmsuch as polyimide is coated. Then, a spacer material is sprayed on oneof the TFT substrate 19 and the film substrate 26 and a seal material iscoated on an outer region other than a display region of the other.Thereafter, both of the TFT substrate 19 and the film substrate 26 areadhered each other to have a gap and then TN-type liquid crystal ispoured into the gap between two substrates 19 and 26 so that a liquidcrystal layer 30 is formed. The liquid crystal is driven by the counterelectrode 29 and the pixel electrode 31 via the TFT 32. Thus, a liquidcrystal panel is formed.

The liquid crystal panel is sandwiched by a pair of polarizers 16 and17. A backlight 6 is provided on the side of the polarizer 17 opposingto the TFT substrate 19. A driving circuit for driving the liquidcrystal 30 and a detecting circuit for detecting a position orcoordinate contacted by the input pen are omitted from the figure. Theoperation of the driving circuit is the same as in a conventional liquidcrystal display apparatus. Also, the operation of the detecting circuitis the same as in the conventional tablet apparatus. For instance, thetechnique disclosed in Japanese Laid Open Patent Disclosure (JP-A-Heisei4-195624) can be applied.

In this manner, the tablet integrated type liquid crystal displayapparatus is produced. In this case, the liquid crystal displayapparatus is viewed from th e side of the film substrate 26.

An input pen 1 is used to input a data or instruction. A system usingelectrostatic capacitor coupling or electromagnetic induction betweenthe input pen 1 and the tablet electrode layer 27 can be used for thepen input. For instance, an example of the electrostatic capacitorcoupling system is described in U.S. Pat. No. 4,853,498 issued toMeadows et al. The description is incorporated herein by reference. Itis desirable that another special pen input panel is not required inaddition to the liquid crystal panel. However, if the film substrate 26is used, a resistive film system may be applied to the tablet integratedtype liquid crystal display apparatus, because the film substrate 26 isthin.

As described above, because the film substrate 26 is made very thin, theparallax between the tip of the input pen 1 and a display image on thedisplay panel can be almost eliminated. Further, because the TFT isproduced on the thick TFT substrate 19 opposing to the film substrate 26which is located on the viewing side, the occurrence of bending of thesubstrate and damage of the TFT can be prevented.

Next, a tablet-integrated-type liquid crystal display apparatusaccording to the second embodiment of the present invention will bedescribed below. FIG. 5 is a cross sectional view illustrating thestructure of the tablet integrate type liquid crystal display apparatusaccording to the second embodiment of the present invention. The liquidcrystal display apparatus is a reflection type apparatus using an activematrix driving system. In the liquid crystal display apparatus, phasetransit type guest host (GH) liquid crystal.

The tablet integrated liquid crystal display apparatus in the secondembodiment has the structure similar to that of the first embodiment.The insulating layer 28 of polyimide is coated onto the TFT 32 array andunevenness is formed on the insulating layer 28 by a usual photoresistprocess. The pixel electrode 31 is formed on the insulating layer 28.The pixel electrode 31 is connected to the corresponding TFT 32 via acontact hole. Because the pixel electrode 31 is also used as areflection plate, the pixel electrode 31 is formed of metal such asaluminum (A1). Any polarizer is not required on either side of theliquid crystal display panel because the GH liquid crystal is used.Further, the backlight is not provided because the display panel is areflection type. The other structural portions are the same as those ofthe first embodiment.

As described above, in the tablet integrated type liquid crystal displayapparatus in the second embodiment, because the pixel electrode 31 whichis used as the reflection plate is provided in the liquid crystal panel,there is not a parallax between the reflection plate and the displayimage as in the conventional example. As a result, there is no case thatthe data or image is displayed in a floating state. Also, the parallaxbetween the display image and the tip of the input pen 1 can be almosteliminated, as in the first embodiment. Further, the occurrence ofbending of the TFT substrate 29 and damage of the elements can beprevented.

In the first and second embodiment, the TFT is used as the switchingelement. However, the same effect can be obtained in the active matrixdriving type, and tablet integrated type liquid crystal displayapparatus using a 2-terminal element such as an MIM or TFD. This isapplied to the following embodiments, too.

Next, the tablet integrated type liquid crystal display apparatusaccording to the third embodiment of the present invention will bedescribed. In the following description, an example in which the presentinvention is applied to a color liquid crystal display of 24 cm in adiagonal direction which has 640×480 RGB dots.

FIG. 6 is a cross sectional view illustrating the structure of thetablet integrated type liquid crystal display apparatus in the thirdembodiment of the present invention. Referring to FIG. 6, a GH-typeliquid crystal 5 is sandwiched by a transparent TFT substrates 3 and atransparent counter electrode substrate 4 and is sealed between them. Ona surface of the TFT substrate 3 opposing to the substrate 4, 480scanning lines, 1920 signal lines, 921600 thin film field effecttransistors (TFT) and pixel electrodes are formed. On the other hand, ona surface of the substrate 4 opposing to the TFT substrate 3 with acolor filter, counter electrodes of ITO are formed. Voltage is appliedto the GH type liquid crystal 5 by the pixel electrode and the counterelectrode via the TFT. The circuit structure of the tablet integratedtype liquid crystal display apparatus in the third embodiment is shownin FIG. 7. The GH liquid crystal layer 5 is connected to thecorresponding TFT, the data driver and a common power supply in series.The gate of the TFT is connected to a gate driver.

The operation principle to display an image in the third embodiment isthe same as that of a conventional transmissive type active matrixdriving type liquid crystal display apparatus.

A tablet device 2 is provided on the other surface of counter electrodesubstrate 4. On a surface of a glass substrate (not illustrated in FIG.6) of the tablet apparatus 2, ITO electrodes (not illustrated in FIG. 6)are formed to detect a position on which input pen 1 is put. A backlightfor illumination is provided on the side of the other surface of the TFTsubstrate 3.

On the other hand, input to the tablet device 2 is performed by makingthe input pen 1 contact the tablet device 2. For instance, two resistivefilms are made to contact with each other and the contact position isdetected. In this case, the tablet device 2 and the counter electrodesubstrate 4 are pushed because of pushing pressure so that the gap widthbetween the TFT substrate 3 and the counter electrode substrate 4changes. As a result, the thickness of the GH liquid crystal layerchanges. However, because the transmissivity of the GH liquid crystaldoes not change so much, a problem in case of practical use does notoccur.

FIG. 8 is a graph illustrating the transmissivity change characteristicsof the GH liquid crystal and the TN liquid crystal. In this graph, asolid line illustrates a simulation result of a transmissivity ratiobetween the case where a voltage is applied to the GH liquid crystallayer having the thickness of 5 μm and the case where the same voltageis applied to the GH liquid crystal layer having the thickness of 4 μmas the result of the pushing pressure. A dashed line illustrates asimulation result of a transmissivity ratio in the same cases. Forinstance, when the voltage of about 2 V is applied to the TN liquidcrystal layer for a gray gradation, the display image changes greatly ifthe TN liquid crystal layer is changed from 5 μm to 4 μm in thickness.However, it could be seen that the display image does not change so muchin the GH liquid crystal layer. The change in the transmissivity in theTN liquid crystal layer is twice in the GH liquid crystal layer.Further, the TN liquid crystal has contrast one order higher than the GHliquid crystal. Therefore, in the case of using the TN liquid crystal,the change of the display image in contrast before and after the liquidcrystal panel is pushed is remarkable. However, in the tablet integratedtype liquid crystal display panel using the GH liquid crystal, there isnot such a problem in practice use.

In the third embodiment, an example is described in which resistivefilms are contacted with each other. However, the tablet device is notlimited to this. For instance, electrostatic capacitive coupling betweenthe input pen 1 and the transparent ITO electrode may be used fordetection of a coordinate in the tablet device 2. Alternatively, it ispossible to apply to the tablet device the method which detects acoordinate using the electromagnetic coupling between the input pen 1and the tablet device 2. In this case, the tablet device 2 is preferablyprovided rear the backlight 6.

Next, the tablet integrated type liquid crystal display apparatusaccording to the fourth embodiment will be described below. In thefollowing description, an example in which the present invention isapplied to a color liquid crystal display of 24 cm in a diagonaldirection which has 640×480 RGB dots.

FIG. 9 is a cross sectional view illustrating the structure of thetablet integrate type liquid crystal display apparatus in the fourthembodiment of the present invention. Referring to FIG. 9, a GH-typeliquid crystal 5 is sandwiched by a transparent TFT substrates 3 and atransparent counter electrode substrate 4 and is sealed between them. Ona surface of the TFT substrate 3 opposing to the substrate 4, 480scanning lines, 1920 signal lines, 921600 thin film field effecttransistors (TFT) and pixel electrodes are formed. The pixel electrodesare connected to the corresponding to the TFTs. Reflection plates 7 ofaluminum are provided above the pixel electrodes 7. On the other hand,on a surface of the substrate 4 opposing to the TFT substrate 3 with acolor filter, counter electrodes of ITO are formed. Voltage is appliedto the GH type liquid crystal 5 by the pixel electrode and the counterelectrode via the TFT.

A tablet device 2 is provided on the other surface of counter electrodesubstrate 4. On a surface of a glass substrate (not illustrated) of thetablet apparatus 2, an ITO electrodes (not illustrated) are formed todetect a position on which an input pen 1 is put. Because the liquidcrystal display apparatus is a reflection type, any backlight 6 is notprovided on the side of the other surface of the TFT substrate 3.

The operation principle to display an image in the third embodiment isthe same as that of a conventional transmissive type active matrixdriving type liquid crystal display apparatus.

On the other hand, input to the tablet device 2 is performed by makingthe input pen 1 contact the tablet device 2. In this case, the tabletdevice 2 and the counter electrode substrate 4 are pushed because ofpushing pressure so that the gap width between the TFT substrate 3 andthe counter electrode substrate 4 changes. As a result, the by thicknessof the GH liquid crystal layer changes. However, because thetransmissivity of the GH liquid crystal does not change so much, aproblem in case of practical use does not occur, as described above.

In the fourth embodiment, an example is described in which there may beused the method which detects a coordinate from the change of theresistance value when an electrode is pressed. However, the tabletdevice is not limited to this. Alternatively, electrostatic capacitivecoupling between the input pen 1 and the transparent ITO electrode maybe used for detection of a coordinate in the tablet device 2. Also, itis possible to apply to the tablet device the method which detects acoordinate using the electromagnetic coupling between the input pen 1and the tablet device 2. In this case, the tablet device 2 is preferablyprovided rear the TFT substrate 3.

Next, the tablet integrated type liquid crystal display apparatusaccording to the fifth embodiment of the present invention will bedescribed. In the following description, an example in which the presentinvention is applied to a color liquid crystal display of 24 cm in adiagonal direction which has 640×480 RGB dots.

FIG. 10 is a cross sectional view illustrating the structure of thetablet integrated type liquid crystal display apparatus in the fifthembodiment of the present invention. Referring to FIG. 10, a GH typeliquid crystal 5 is sandwiched by a transparent TFT substrates 3 and atransparent counter electrode substrate 4 and is sealed between them. Ona surface of the TFT substrate 3 opposing to the substrate 4, 480scanning lines, 1920 signal lines, 921600 thin film field effecttransistors (TFT) and pixel electrodes are formed. On the other hand, ona surface of the substrate 4 opposing to the TFT substrate 3 with acolor filter, counter electrodes of ITO are formed. Voltage is appliedto the GH type liquid crystal 5 by the pixel electrode and the counterelectrode via the TFT.

Tablet electrodes 8 of ITO are provided on the other surface of counterelectrode substrate 4 to detect a position on which an input pen 1 isput. A protecting film 9 is provided on the tablet electrodes 8 toprotect the tablet electrodes 8 from damage due to contact with theinput pen 1. A backlight 6 for the illumination is provided on the sideof the other surface of the TFT substrate 3.

The operation principle to display an image in the third embodiment isthe same as that of a conventional transmissive type active matrixdriving type liquid crystal display apparatus. On the other hand, inputto the tablet device 2 is performed by making the input pen 1 contactthe tablet device 2. In this case, the tablet device 2 and the counterelectrode substrate 4 are pushed because of pushing pressure so that thegap width between the TFT substrate 3 and the counter electrodesubstrate 4 changes. As a result, the thickness of the GH liquid crystallayer changes. However, because the transmissivity of the GH liquidcrystal does not change so much, a problem in case of practical use doesnot occur, as described above.

In the fifth embodiment, an example is described in which electrostaticcapacitive coupling between the input pen 1 and the transparent ITOelectrode is used for detection of a coordinate. However, the presentinvention is not limited to this, but there may be used the method whichdetects a coordinate from the change of the resistance value when anelectrode is pressed. Also, the method may be used in which thepotential of a tablet electrode 8 is detected by the input pen 1 todetect a coordinate.

Next, the tablet integrated type liquid crystal display apparatusaccording to the sixth embodiment will be described below. In thefollowing description, an example in which the present invention isapplied to a color liquid crystal display of 24 cm in a diagonaldirection which has 640×480 RGB dots.

FIG. 11 is a cross sectional view illustrating the structure of thetablet integrate type liquid crystal display apparatus in the sixthembodiment of the present invention. Referring to FIG. 11, a GH-typeliquid crystal 5 is sandwiched by a transparent TFT substrates 3 and atransparent counter electrode substrate 4 and is sealed between them. Ona surface of the TFT substrate 3 opposing to the substrate 4, 480scanning lines, 1920 signal lines, 921600 thin film field effecttransistors (TFT) and pixel electrodes are formed. The pixel electrodesare connected to the corresponding to the TFTs. Reflection plates 7 ofaluminum are provided above the pixel electrodes 7. On the other hand,on a surface of the substrate 4 opposing to the TFT substrate 3 with acolor filter, counter electrodes of ITO are formed. Voltage is appliedto the GH type liquid crystal 5 by the pixel electrode and the counterelectrode via the TFT. On the other surface of the counter electrodesubstrate 4, tablet electrodes 8 of ITO are provided to detect aposition on which an input pen 1 is put. A protection film 9 is providedto protect the tablet electrodes 8 from damage due to contact with theinput pen 1. Because the liquid crystal display apparatus is areflection type, any backlight 6 is not provided on the side of theother surface of the TFT substrate 3.

The operation principle to display an image in the third embodiment isthe same as that of a conventional transmissive type active matrixdriving type liquid crystal display apparatus.

On the other hand, input to the tablet device 2 is performed by makingthe input pen 1 contact the tablet device 2. In this case, the tabletdevice 2 and the counter electrode substrate 4 are pushed because ofpushing pressure so that the gap width between the TFT substrate 3 andthe counter electrode substrate 4 changes. As a result, the thickness ofthe GH liquid crystal layer changes. However, because the transmissivityof the GH liquid crystal does not change so much, a problem in case ofpractical use does not occur, as described above.

In the fourth embodiment, an example is described in which electrostaticcapacitive coupling between the input pen 1 and the transparent ITOelectrode is used for detection of a coordinate in the tablet device 2.However, the tablet device is not limited to this, but there may be usedthe method which detects a coordinate from the change of the resistancevalue when an electrode is pressed. Also, it is possible to apply to thetablet device the method which detects a coordinate using theelectromagnetic coupling between the input pen 1 and the tablet device2. In this case, the tablet device 2 is preferably provided rear the TFTsubstrate 3.

Next, the tablet integrated type liquid crystal display apparatusaccording to the seventh embodiment will be described below. In thefollowing description, an example in which the present invention isapplied to a color liquid crystal display of 24 cm in a diagonaldirection which has 640×480 RGB dots.

FIG. 12 is a cross sectional view illustrating the structure of thetablet integrate type liquid crystal display apparatus in the seventhembodiment of the present invention. Referring to FIG. 12, a GH-typeliquid crystal 5 is sandwiched by a transparent TFT substrates 3 and atransparent counter electrode substrate 4 and is sealed between them. Ona surface of the TFT substrate 3 opposing to the substrate 4, tabletelectrodes 10 are provided to use for detection of a coordinate pointedby the input pen 1. Above the tablet electrodes 10 via an insulatingfilm (not shown), 480 scanning lines, 1920 signal lines, 921600 thinfilm field effect transistors (TFT) and pixel electrodes are formed. Thepixel electrodes are connected to the corresponding to the TFTs.Reflection plates 7 of aluminum are provided above the pixel electrodes7. On the other hand, on a surface of the substrate 4 opposing to theTFT substrate 3 with a color filter, counter electrodes of ITO areformed. Voltage is applied to the GH type liquid crystal 5 by the pixelelectrode and the counter electrode via the TFT. On the other surface ofthe counter electrode substrate 4, a tablet device 2 is provided todetect a position on which an input pen 1 is put. Because the liquidcrystal display apparatus is a reflection type, any backlight 6 is notprovided on the side of the other surface of the TFT substrate 3.

The operation principle to display an image in the third embodiment isthe same as that of a conventional reflection type active matrix drivingtype liquid crystal display apparatus.

On the other hand, input to the tablet device 2 is performed by makingthe input pen 1 contact the tablet device 2. In this case, the tabletdevice 2 and the counter electrode substrate 4 are pushed because ofpushing pressure so that the gap width between the TFT substrate 3 andthe counter electrode substrate 4 changes. As a result, the thickness ofthe GH liquid crystal layer changes. However, because the transmissivityof the GH liquid crystal does not change so much, a problem in case ofpractical use does not occur, as described above.

In the fourth embodiment, an example is described in which a coordinateis detected using the electromagnetic coupling between the input pen 1and the tablet electrode 8.

Next, the tablet integrated type liquid crystal display apparatusaccording to the eighth embodiment of the present invention will bedescribed. In the following description, an example in which the presentinvention is applied to a color liquid crystal display of 24 cm in adiagonal direction which has 640×480 RGB dots.

FIG. 13 is a cross sectional view illustrating the structure of thetablet integrated type liquid crystal display apparatus in the eighthembodiment of the present invention. Referring to FIG. 13, a GH-typeliquid crystal 5 is sandwiched by a transparent TFT substrates 3 and atransparent counter electrode substrate 4 and is sealed between them. Ona surface of the TFT substrate 3 opposing to the substrate 4, 480scanning lines, 1920 signal lines, 921600 thin film field effecttransistors (TFT) and pixel electrodes are formed. On the other hand, ona surface of the substrate 4 opposing to the TFT substrate 3 with acolor filter, tablet electrodes 11 are provided to detect a position onwhich an input pen 1 is put. Counter electrodes of ITO are formed abovethe tablet electrodes 11 via an insulating film. Voltage is applied tothe GH type liquid crystal 5 by the pixel electrode and the counterelectrode via the TFT. A backlight 6 for the illumination is provided onthe side of the other surface of the TFT substrate 3.

The operation principle to display an image in the third embodiment isthe same as that of a conventional transmission type active matrixdriving type liquid crystal display apparatus. On the other hand, theinput pen 1 is made to contact the counter electrode substrate 4. Inthis case, the counter electrode substrate 4 is pushed because ofpushing pressure so that the gap width between the TFT substrate 3 andthe counter electrode substrate 4 changes. As a result, the thickness ofthe GH liquid crystal layer changes. However, because the transmissivityof the GH liquid crystal does not change so much, a problem in case ofpractical use does not occur, as described above.

In the eighth embodiment, an example is described in which electrostaticcapacitive coupling between the input pen 1 and the transparent ITOelectrode is used for detection of a coordinate. However, the presentinvention is not limited to this, but the method may be used in whichthe potential of a tablet electrode 8 is detected by the input pen 1 todetect a coordinate.

Next, the tablet integrated type liquid crystal display apparatusaccording to the ninth embodiment of the present invention will bedescribed. In the following description, an example in which the presentinvention is applied to a color liquid crystal display of 24 cm in adiagonal direction which has 640×480 RGB dots.

FIG. 14 is a cross sectional view illustrating the structure of thetablet integrated type liquid crystal display apparatus in the ninthembodiment of the present invention. Referring to FIG. 14, a TN-typeliquid crystal 24 is sandwiched by a transparent TFT substrates 3 and atransparent counter electrode substrate 4 and is sealed between them. Ona surface of the TFT substrate 3 opposing to the substrate 4, 480scanning lines, 1920 signal lines, 921600 thin film field effecttransistors (TFT) and pixel electrodes are formed. On the other hand, ona surface of the substrate 4 opposing to the TFT substrate 3 with acolor filter, counter electrodes of ITO are formed. Voltage is appliedto the TN type liquid crystal 5 by the pixel electrode and the counterelectrode via the TFT.

A tablet device 2 is provided on the other surface of the counterelectrode substrate 4. A backlight 6 for the illumination is provided onthe side of the other surface of the TFT substrate 3.

After the TFT substrate 3 is formed by the same method as in theconventional technique, a polyimide film is formed on it. The polyimidefilm is patterned into a plurality of rectangular shapes by aphoto-lithography method so that a plurality of supports 25 are formed.The supports 25 are provided to avoid the pixel electrodes with theperiod as much as the pixel pitch.

The operation principle in the present embodiment for displaying animage is same as the case of the active matrix-type liquid crystaldisplay apparatus of the conventional transmission type. On the otherhand, input to the tablet device 2 is performed using the input pen 2.At this time, the tablet device 2 and the counter electrode substrate 4are pushed because of pushing pressure. However, because the supports 25are inserted between the counter electrode substrate 4 and the TFTsubstrate 3 with the very short period, the gap width of TN-type liquidcrystal layer 24 changes hardly. Even if the change occurs, the changeis within one pixel because the supports 25 are provided with the periodas long as the pixel period. Therefore, a problem does not occur in caseof practical use.

In the above example, the supports 25 which connect the counterelectrode substrate 3 and the TFT substrate 4 are formed of thepolyimide film by the photo-lithography method. However, the presentinvention is not limited to this. Other means may be used if a materialand structure are selected such that the gap width of the liquid crystallayer is not changed because of the pushing pressure so that the displayimage is not degraded.

In the present embodiment, the case that the supports are rectangularwas described. However, the shape of the support may be different ifthere is no problem in the pouring and orientation of liquid crystal.Further, it was described that the supports 25 are arranged with theperiod as long as the pixel pitch. However, if the change of the gapwidth of the liquid crystal layer is so small that the degradation of adisplay image is not sensitive to a user, the period may be extended orshortened. Alternatively, the supports 25 may be arranged randomly.

As described above, according to the present invention, because aprotection board is not necessary which is inserted between the liquidcrystal display and the tablet not to change the gap width of the liquidcrystal layer, the weight of the tablet integrated type liquid crystaldisplay apparatus can be reduced 20%.

Also, the thickness of the display apparatus can be reduced to abouthalf of that of the conventional display apparatus. Further, because thethick protection board is not inserted between the tip and the displayapparatus, it is possible to realize the display apparatus with noparallax.

Also, according to the present invention, the glass substrate is usedfor the TFT substrate and the plastic film substrate having thethickness equal to or less than 0.6 mm is used for the counter electrodesubstrate. In addition, the counter electrode substrate is arranged onthe viewing side. Therefore, the parallax between the display image andthe tip of the input pen input can be almost eliminated. Further, theoccurrence of bending of the TFT substrate and damage of the elementssuch as the TFTs can be prevented.

If the present invention is applied to the personal computer displayhaving 480×640 RGB dots, a tablet integrated type liquid crystal displayapparatus can be achieved to have the resolution of about 200 μm and toreduce the weight and the thickness.

What is claimed is:
 1. A liquid crystal display apparatus comprising: a pixel electrode substrate having a plurality of pixel electrodes arranged in a matrix; a counter electrode substrate having at least one electrode arranged in correspondence to said plurality of pixel electrodes; and a guest-host liquid crystal layer interposed between said pixel electrode substrate and said counter electrode substrate, wherein said pixel electrode substrate is composed of a glass substrate, and said counter electrode substrate is composed of a plastic film having a thickness equal to or less than 0.6 mm, said counter electrode substrate is provided on a viewer side, whereby change in transmissivity ratio with change in spacing between said counter electrode and said pixel electrode due to bending of said counter electrode substrate is limited while parallax across said counter electrode substrate is substantially eliminated, and wherein each of said plurality of pixel electrodes is composed of a metal reflection electrode.
 2. The liquid crystal display apparatus according to claim 1, where said pixel electrode substrate has an insulating film with uneven portions, and said pixel electrode substrate is formed on or above said uneven portions of said insulating film. 